package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class simpleExecutor implements Exeuctor {
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException, IntrospectionException, InvocationTargetException, InstantiationException {
        //注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();
        //获取sql语句   select * from user where id = #{id} and username = #{username}
        //转换为  select * from user where id = ? and username = ?
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);
        //获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        //设置参数
            //获取到了参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterTypeClass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = paramterTypeClass.getDeclaredField(content);
            //暴力访问，防止私有化
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1, o);
        }
        //执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        ArrayList<Object> objects = new ArrayList<>();
        //封装返回结果集
        while (resultSet.next()){
            Object o = resultTypeClass.newInstance();
            //取出元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段的值
                Object value = resultSet.getObject(columnName);
                //使用反射或者内省，根据数据库表和实体的对应关系，完成映射
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }


    /**
     *  更新 or 插入 or 删除，由传入的 MappedStatement 的 SQL 所决定
     * @param ms
     * @param parameter
     * @return
     * @throws SQLException
     */
    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception  {
        Statement stmt = null;
        Connection connection = configuration.getDataSource().getConnection();
        //获取sql语句
        String sql = mappedStatement.getSql();
        //转换为
        BoundSql boundSql = getBoundSql(sql);
        //获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        //设置参数
        //获取到了参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterTypeClass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = paramterTypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);

            preparedStatement.setObject(i+1, o);
        }
        // 执行 StatementHandler ，进行写操作
        return preparedStatement.executeUpdate();
    }


    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if(paramterType != null){
            Class<?> aClass = Class.forName(paramterType);
            return aClass;

        }
        return  null;
    }

    /**
     * 1.完成对#{}的解析工作，将#{}使用？进行代替，2.解析出#{}里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql){
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}",parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        return boundSql;

    }


}
